Actinic Keratosis (AK) is a skin disorder that creates hard, wart-like surfaces. Long-term sun exposure makes skin patchy, spotty, and rough. Non-melanoma skin cancers and AK are not well-understood. The correlation of Keratosis with melanocytic naevi is not clear either. This study investigates the risk factors of AK. The objective is to find out if AK can coexist with NMSC and melanoma.

The constitutional and exposure factors that lead to AK are the primary factor under analysis. A controlled study took place in multiple hospitals in Finland, Malta, Germany, Italy, Greece, Poland, Spain, and Scotland. There were 343 AK patients, and 409 and 602 patients with squamous and basal carcinomas. There were 360 with invasive melanoma, while 119 had in situ melanoma. The study also had 686 control subjects. Both patient and dermatologist questionnaires collected exposure data. Unconditional logistic regression modeling assessed the AK risk associations. They included sun exposure habits, certain drugs, the influence of phenotype characteristics, and the presence of naevi.

Subjects with darker skin have a lower risk for AK. Overall, the naevi number and educational level have an inverse link with AK. Sun exposure, diuretic drugs, and cardiac medicines increased AK’s risk. The chances of coexistence of AK with SCC, BCC, in situ, and invasive melanoma are 58%, 30%, 12%, and 6%. Those with red hair have 7 times higher risk of AK. In comparison, brown-eyed subjects have a 40% reduced risk as compared to those with blue eyes.

This large scale study confirmed the well-known AK risk associations. New risks like cardiac and diuretic drugs open up new possibilities for further research.